In electronics, the voltage across an electrically resistive circuit portion is equal to the product of multiplying its resistance R (ohms) times the amount of electric current I (amperes) flowing through it according to Ohm's Law. Resistance reduces voltage magnitude at points farther into a circuit from a point of application of voltage, so this voltage reduction is called IR drop.
For instance, a power supply voltage designated VDD can be applied, and a geometric structure of connected electrical conductors called the power grid of the integrated circuit provides paths for electric currents to flow to many particular locations in the integrated circuit. However, as the electric currents flow to various powered circuit portions at or on the way to the particular locations or beyond the locations, various IR drops are inherently introduced and diminish the voltage at any given particular location relative to VDD.
An integrated circuit chip device in manufacture or in the field can be operated to test it and/or operated to use the device for its intended functions. These ways of operation are called test mode and functional mode scenarios respectively.
Analog electronic circuits can have a variety of varying voltages across transistors and other components that can vary anywhere across a range of voltages. By contrast, digital electronic circuits have transistors operating as switching circuits the voltage across which approximately switches, or toggles, between just two voltage levels for instance. Electronic test equipment called a tool(s) tests an integrated circuit and dumps out values from the integrated circuit for further analysis. The information gathered by the test equipment is analyzed in the test equipment or elsewhere externally by various analysis methods.
IR drop in the chip can lead to reduction in device performance. This is true in both functional and test scenarios. Different ways of estimating IR drop in the device exist and depend on the tools and analysis methods. It is believed that many of the tools take some kind of value change dump (VCD) or the like to annotate the total activity in the nodes. But the number of VCDs, and the accuracy of the VCDs, are likely to depend on the understanding or insight of the designers with regard to the use-case.
Conventional methodology of IR drop detection has limitations. Industry standard tools are used to estimate and detect IR drop in an integrated circuit chip design. Functional/test use case scenarios are applied and taken and a value change dump file (VCD) is generated for them. This VCD is taken as an input to the tool which takes the toggle activity and provides an estimate of the IR drop in different locations in the design.
A drawback in this approach is that the data dump is only done for some scenarios that are known to the user or designer and may not cover all actual possibilities. The worst case estimate based on the VCD may not be accurate because it depends on the usage, i.e. how and which circuits in the chip are actually operated in the scenarios applied, because the amounts and distribution of electric currents around the chip, and therefore the IR drops, result from that actual operation.
In view of the above problems, it would be desirable to somehow provide solutions in this field that can address the problems and be economical in terms of chip real estate, test time and test complexity, that can offer wide applicability to various kinds of integrated circuits, and that can provide other advantages in realistic, short-cycle industrial design and productization environments.